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COMBINATORIAL SCREENING METHODS FOR METAL CATALYSTS
AND
CYCLOMETALATED IRIDIUM AND PLATINUM COMPLEXES
WITH NON-INNOCENT LIGANDS
by
Bhavna Hirani
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(CHEMISTRY)
May 2007
Copyright 2007
Bhavna Hirani

Techniques are developed for the combinatorial screening of metal catalysts towards the oxidation of water. The electrochemical reaction is thermodynamically feasible but kinetically labile at the anode. The use of metal particles as catalysts at the anode can lower the overpotential for the reaction. Thermal output method of combinatorial screening is explored as a qualitative and fast measurement of activity of platinum-group catalysts. The activity is monitored as a function of the heat dissipated across a fixed resistor in series with the cell. The more active a catalyst, a larger current flows through the cell for the same applied potential resulting in a larger dissipation of heat across the resistor that is imaged by an infrared camera as greater heating. The choice of electrolytes is also explored. The preparation of metal catalyst using thermal reduction of metal precursor solutions is described. The catalytic surface is characterized by microscopy (SEM) and spectroscopy (XPS).; The set up of instrumentation for a combinatorial array of metal particles for the thermal output method is described. The optimization of system parameters is listed. The data is presented qualitatively as thermal images and in some quantitative results from the analysis of thermal counts. Comparative studies with individual measurements provide an estimate of overpotential required for oxidation of water. The limitations of thermal screening method are discussed.; Combinatorial screening using visual output, as a more quantitative method than thermal output, is experimented for the activity of metal catalysts. The method is based on the amplification of current through the cell such that small differences in the activity of metal particles can be observed by monitoring the brightness of LED in the circuit. It is made possible by the use of a potentiostat and an ammeter for each. It is shown useful in rating the activity of some of the platinum group metals as catalysts for the oxidation of water. It also compares very well to individual measurements in the same setup using a standard laboratory potentiostat.; The coordination chemistry of cyclometalated iridium and platinum metal complexes with a dioxolene-type non-innocent ligand is discussed with interest in tuning the low-energy transitions. The synthesis and characterization, electronic and electrochemical properties of these open-shell complexes is described. Theoretical studies using both density functional methods and time-dependent density functional methods are given. The iridium and platinum metal complexes are compared through structural, spectroscopic, and electrochemical properties to related complexes of ruthenium and osmium.; The electronic properties of an iridium dinuclear complex are studied and compared to the mononuclear analog. The synthesis and characterization, electronic and electrochemical properties of the complex is described. The results from timedependent density functional calculations are presented as significant to the discussion on isomers of the complex.

COMBINATORIAL SCREENING METHODS FOR METAL CATALYSTS
AND
CYCLOMETALATED IRIDIUM AND PLATINUM COMPLEXES
WITH NON-INNOCENT LIGANDS
by
Bhavna Hirani
A Dissertation Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(CHEMISTRY)
May 2007
Copyright 2007
Bhavna Hirani